In international Journal of Food Science and Technology 41, p. 569-575 (2006), Ismail S. Dogan defines a wafer as low-moisture-baked foods being formed from a batter and baked between hot plates. It is further disclosed that the quality of wafer sheets is mainly controlled by flour property, water level and temperature, mixing action, baking time and temperature. The quality of the wafer is a result of attributes of the batter such as the density, viscosity, holding time and temperature, and by properties of the wafer such as weight, surface colour, fragility and moisture content. The study concludes that wafers have little in common with other types of biscuits in regard to the formulae and processing, and that water level and gluten content are important for obtaining a high-quality wafer sheet.
Duncan Manley disclose in the book “Technology of biscuits, crackers and cookies” (p. 296, 3rd Ed, Woodhhead Pub. Ltd.) that creation of gas cells in gelatinised starch is most important in wafer manufacture. Although bubbles of air are included during batter mixing most of these float out of the batter before it deposited onto the plates. If the conditions are such that insufficient time is allowed for the bubbles to leave the batter it could be that the density of the batter changes during use and this will affect the baked sheet weights in terms of giving variable and uncontrolled texture. He further states that chemical aeration is usually achieved with sodium bicarbonate or ammonium bicarbonate or a mixture of the two. Ammonium bicarbonate is particularly effective. Experience has shown that attention to the combination of batter consistency and ammonium bicarbonate level is the best way to control batter spread and wafer sheet weight. Increasing the amount of these aeration chemicals increases the aeration, but again the texture of the wafer will be un-processable above a certain level, by which time the distinct and unpleasant off-flavour given by these chemicals becomes unpleasant and unpalatable for a foodstuff. The use of yeast as a method of aeration by the creation of carbon dioxide in the batter during fermentation is steeped in tradition. Batter standing time and suitable temperatures to allow multiplication of the yeast are not usually very practical in modern mixing and batter-handling systems, especially when producing wafer on an industrial scale. Yeast is now rarely used in batter recipes.
It is known that adding extra water to a wafer batter mix will reduce the effective density of a wafer sheet. In the process of baking any wafer from water based batter, when the batter is heated the water turns to steam, the steam forms bubbles in the mix and these bubbles then form the cavities/cells in the wafer structure. The more water there is in a batter, the more steam is generated, and the steam generates more cavities/cells in the final wafer resulting in the batter having a reduced density. The outer layers of the wafer are also thinner which gives the wafer a lighter texture. Low density wafers give a lightness and crispiness to some wafer products that is desirable to the consumer.
However, there is a lower limit to the effective density of finished wafer that this method makes. As more and more water is added, the structure of the cavities/cells that are generated becomes less uniform throughout the wafer as tie process of the formation of the cells by the steam is not well regulated or controlled. A wafer made in such a way is fragile due to the irregular cell structure and large cells that extend through the wafer.
Additionally, as more water is added to the batter mix, it is more difficult to control the process and bake wafers of consistent quality. Another added complication is that, if more water is added to the batter, then the viscosity, of the batter decreases and it becomes difficult to handle and deposit a low viscosity liquid onto the baking plates. Unwanted dripping of the batter will occur at the point of deposition causing waste and oven fires.
The result of these methods of producing very light wafers through the use of high dilution or high addition of aeration chemicals wafers is an inhomogeneous content of cavities/cells which reduces robustness and causes breakage when subjected to further handling, such as simple removal from the baking plate.
Aeration by these well-known methods therefore has ids limits before the quality of the wafer terms of texture and flavour is compromised, and also becomes too fragile to handle in the industrial process, such as simple removal from the baking plate. Low density wafers of density <0.16 g/cm3 are therefore rot known in existing technology.